pip在Mac OSX 10.10.2上安装模块错误

Question

我正在尝试使用ipython安装pip。

sudo pip install ipython

我收到以下错误：

Traceback (most recent call last):
  File "/usr/local/bin/pip", line 5, in <module>
    from pkg_resources import load_entry_point
  File "build/bdist.macosx-10.10-x86_64/egg/pkg_resources/__init__.py", line 29, in <module>
  File "build/bdist.macosx-10.10-x86_64/egg/functools.py", line 67, in <module>
    ('__lt__', lambda self, other: not self >= other)]
  File "build/bdist.macosx-10.10-x86_64/egg/_functools.py", line 7, in <module>
  File "build/bdist.macosx-10.10-x86_64/egg/_functools.py", line 4, in __bootstrap__
AttributeError: 'module' object has no attribute 'resource_filename'

以前当我遇到此问题时，重新安装functools修复了问题。

这次我甚至无法使用：

pip list

functools又被打破了吗？